Check if a particular key exists in Java Hashtable example

Hashtable java Collections interview Questions

Check if a particular key exists in Java Hashtable example

Kris Kimcil 22.34 Komentar

1.Basic java example program to check particular element exist in hashtable

• boolean containsKey(Object key)   This method used to check  particular key exist in hashtable

1. package com.CheckElelemtHashtable;
2.  
3. import java.util.Hashtable;
4. import java.util.Iterator;
5.  
6. public class HashtableExample{
7.  
8. public static void main(String[] args) {
9.   
10.  //create Hashtable object
11.        Hashtable<String,String> hashtable = new Hashtable<String,String>();
12.        
13. //add key value pairs to Hashtable
14. hashtable.put("1","Java Interview Questions");
15. hashtable.put("2","Java Interview Programs");
16. hashtable.put("3","Concept and exampe program");
17. hashtable.put("4","Concept and interview Questions");
18. hashtable.put("5","Java Quiz");
19. hashtable.put("6","Real time examples");
20.  
21.  /*
22.  To check whether a particular key exists in Hashtable we need to use
23.  boolean containsKey(Object key) method of Hashtable class.
24. if the Hashtable contains mapping for specified key It returns true
25. otherwise returns false.
26. */
27.        
28.  boolean isExists = hashtable.containsKey("5");
29.  System.out.println("5 exists in Hashtable ? : " + isExists);
30. 
    
31.  
32.  
33. Enumeration e=hashtable.elements();
34.           
35.  System.out.println("Display result:"); 
36.            
37. // display search result
38.  while (e.hasMoreElements()) {
39.         System.out.println(e.nextElement());
40. }    
41. 
    
42. }
43.  
44. }
     

Output:

1. 5 exists in Hashtable ? : true
2. Hashtable values : 
3. Display result:
4. Real time examples
5. Java Quiz
6. Concept and interview Questions
7. Concept and exampe program
8. Java Interview Programs
9. Java Interview Questions

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Non static blocks in java example

Core java Interview Questions

Non static blocks in java example

Kris Kimcil 04.17 Komentar

Non Static Blocks in java

• When ever object created non static blocks will be executed before the execution of constructor
• Non static blocks are class level block which does not have prototype

1. package nonstaticblocks;
2. public class A {
3.  
4.    {
5.         
6.        System.out.println("non static block executed");
7.  
8.     }
9.  
10. }

What is the need of Non static blocks in java?

• To execute any logic whenever object is created irrespective of constructor used in object creation.

Who will execute Non static blocks?

• Non static blocks are automatically called by JVM for every object creation in java stack area

How many Non static blocks we can create?

• We can create any number of Non static blocks

Order of execution of non static blocks

• Order of execution of non static blocks will be order as they are defined.

1. package nonstaticblocks;
2. public class A {
3.  
4. {
5. 
   
6.   System.out.println("first block");
7. } 
8.  
9. {
10.  System.out.println("second block");
11. }
12.  
13. {
14.  System.out.println("third block");
15. }
16. public static void main(String[] args) {
17.   A obj= new A();
18. }
19. }

 Output:

1. first block
2. second block
3. third block

 Order of execution of non static blocks with respect to constructor?

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Remove all elements LinkedHashSet example

java Collections interview Questions LinkedHashSet

Remove all elements LinkedHashSet example

Kris Kimcil 03.41 Komentar

1.Basic java example program to remove all elements in linkedhashset

• clear()   This method used to remove all elements from Linkedhashset.

1. package com.removeelementLinkedhashset;
2.  
3. import java.util.LinkedHashSet;
4. import java.util.Iterator;
5.  
6. public class LinkedHashsetExample{
7.  
8. public static void main(String[] args) {
9.   
10. LinkedHashSet<String> linkedhashset = new LinkedHashSet<>();
11.        
12.         linkedhashset.add("Java Interview Questions");
13.         linkedhashset.add("Java interview program");
14.         linkedhashset.add("Concept and example program");
15.         linkedhashset.add("Concept and interview questions");
16.         linkedhashset.add("Java Quiz");
17.     
18.       
19. System.out.println("LinkedHashSet before removal : " + linkedhashset);
20.  
21.   boolean blnRemoved = linkedhashset.remove("Java Quiz");
22.   System.out.println("Was Java Quiz removed from LinkedHashSet ? " + blnRemoved);
23.   
24. 
    
25.  
26. System.out.println("LinkedHashSet after removal : ");
27.  
28. Iterator it=linkedhashset.iterator();
29.              
30. while(it.hasNext()){
31. System.out.println(it.next());
32.                      
33. }   
34.  linkedhashset.clear();
35.  System.out.println("LinkedHashSet after removal  all elements"); 
36.  
37. }
38.  
39. }
     

Output:

1. LinkedHashSet before removal : [Java Interview Questions, Java interview program, Concept
2. and example program, Concept and interview questions, Java Quiz]
3. Was Java Quiz removed from LinkedHashSet ? true
4. LinkedHashSet after removal :
5. Java Interview Questions
6. Java interview program
7. Concept and example program
8. Concept and interview questions
9. LinkedHashSet after removal all elements  :[]

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Differences between Default constructor and no argument constructor in java

Core java Interview Questions

Differences between Default constructor and no argument constructor in java

Kris Kimcil 03.19 Komentar

Differences between default constructor and no argument constructor

Default Constructor in java:

• When we write a class without any constructor then at compilation time java compiler creates a default constructor in our class.
• The accessibility modifier of the default constructor is same as accessibility modifier of class.
• The allowed accessibility modifier are public and default.
• Default constructor added by java compiler this constructor does not have anything except super(); call.

1. package constructor;
2. public class A {
3.   
4.  
5. }

1. package constructor;
2. public class A {
3.  
4.     A(){
5.         
6.         super();
7.  
8.     }
9.  
10. }

• If our class have any constructor then java compiler does not create default constructor

No-argument Constructor in java:

• As a developer we can create our own constructor with no arguments is known as no-argument constructor.
• It can have all four accessibility modifiers as it is defined by developer.
• So allowed accessibility modifiers are public, private, protected and default
• It can have logic including super call.

1. package constructor;
2. public class A {
3.  
4.     A(){
5.         
6.   super();
7.   System.out.println("no -argument constructor");
8. 
   
9.     }
10.  
11. }

• The common point between default and no-argument constructor 
• Both does not have any arguments.
• And one more point we need to remember that in no-argument constructor also by default first statement will be super() call which is added by java compiler if it does not have.

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Remove specified element from Java LinkedHashSet example

java Collections interview Questions java programs for freshers LinkedHashSet

Remove specified element from Java LinkedHashSet example

Kris Kimcil 02.40 Komentar

1.Basic java example program to remove particular element in linkedhashset

• boolean remove(Object o)    This method used to remove specified element from Linkedhashset.

1. package com.removeelementLinkedhashset;
2.  
3. import java.util.LinkedHashSet;
4. import java.util.Iterator;
5.  
6. public class LinkedHashsetExample{
7.  
8. public static void main(String[] args) {
9.   
10. LinkedHashSet<String> linkedhashset = new LinkedHashSet<>();
11.        
12.         linkedhashset.add("Java Interview Questions");
13.         linkedhashset.add("Java interview program");
14.         linkedhashset.add("Concept and example program");
15.         linkedhashset.add("Concept and interview questions");
16.         linkedhashset.add("Java Quiz");
17.     
18.       
19. System.out.println("LinkedHashSet before removal : " + linkedhashset);
20.  
21.   boolean blnRemoved = linkedhashset.remove("Java Quiz");
22.   System.out.println("Was Java Quiz removed from LinkedHashSet ? " + blnRemoved);
23.   
24. 
    
25.  
26. System.out.println("LinkedHashSet after removal : ");
27.  
28. Iterator it=linkedhashset.iterator();
29.              
30. while(it.hasNext()){
31. System.out.println(it.next());
32.                      
33. }   
34.  
35. }
36.  
37. }
     

Output:

1. LinkedHashSet before removal : [Java Interview Questions, Java interview program, Concept
2. and example program, Concept and interview questions, Java Quiz]
3. Was Java Quiz removed from LinkedHashSet ? true
4. Java Interview Questions
5. Java interview program
6. Concept and example program
7. Concept and interview questions

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Check if a particular element exists in Java LinkedHashSet Example

java Collections interview Questions LinkedHashSet

Check if a particular element exists in Java LinkedHashSet Example

Kris Kimcil 02.25 Komentar

1.Basic java example program to check particular element is exists in linkedhashset

• boolean contains(Object o)  This method Returns true if this set contains the specified element

1. package com.checkelementhashset;
2.  
3. import java.util.LinkedHashSet;
4. import java.util.Iterator;
5.  
6. public class LinkedHashsetExample{
7.  
8. public static void main(String[] args) {
9.   
10. LinkedHashSet<String> linkedhashset = new LinkedHashSet<>();
11.        
12.         linkedhashset.add("Java Interview Questions");
13.         linkedhashset.add("Java interview program");
14.         linkedhashset.add("Concept and example program");
15.         linkedhashset.add("Concept and interview questions");
16.         linkedhashset.add("Java Quiz");
17.     
18.  /*
19.  To check whether a particular value exists in LinkedHashSet we need to use
20.   boolean contains(Object value) method of HashSet class.
21.  this method returns true if the LinkedHashSet contains the value, otherwise returns false.
22.  */
23.        
24.         boolean isExists = linkedhashset.contains("Java Quiz");
25.         System.out.println("Java Quiz exists in LinkedHashSet? : " + isExists);    
26.  
27. 
    
28.  
29. Iterator it=linkedhashset.iterator();
30.              
31. while(it.hasNext()){
32. System.out.println(it.next());
33.                      
34. }   
35.  
36. }
37.  
38. }
     

Output:

1. Java Quiz exists in LinkedHashSet ? : true
2. Java Interview Questions
3. Java interview program
4. Concept and example program
5. Concept and interview questions
6. Java Quiz

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Return statement in finally block in java

exception handling interview questions finally with return

Return statement in finally block in java

Kris Kimcil 00.32 Komentar

Can we write return statement in finally block

• Finally block will executes always excepts system.exit().
• So if we are returning some value in finally means it will be returned always
• Finally will executed so method always returns finally return value and no need of keeping return value at end of the method.
• And in finally after return if we keep some statement those statement will be treated as dead code.

i)Return statement in finally block

1. package com.exceptionhandlingiinterviewquestions;
2.  
3. public class TryCatchReturn{
4.  
5. int calc(){ 
6.         
7. try {
8.  
9. 
   
10.  
11. } catch (Exception e) {
12.  
13. }
14.  finally(){
15.  return 1;
16. }   
17.  System.out.println("End of the method"); // Error : Unreachable code
18. }
19.     
20.     
21. public static void main(String[] args) {
22.         
23.         TryCatchReturn obj = new TryCatchReturn();
24.        
25.  
26. }
27. 
    
28. }
     

ii) return statement in finally

1. package com.exceptionhandlingiinterviewquestions;
2.  
3. public class TryCatchReturn{
4.  
5. int calc(){ 
6.         
7. try {
8.  
9. 
   
10.  
11. } catch (Exception e) {
12.  
13. }
14.  finally(){
15.  return 1;
16. System.out.println("End of the method"); // Error : Unreachable code
17. }   
18.  
19. }
20.     
21.     
22. public static void main(String[] args) {
23.         
24.         TryCatchReturn obj = new TryCatchReturn();
25.        
26.  
27. }
28. 
    
29. }
     

iii) return statement in try catch and finally blocks

1. package com.exceptionhandlingiinterviewquestions;
2.  
3. public class TryCatchReturn{
4.  
5. int calc(){ 
6.         
7. try {
8.  
9. return 10;
10.  
11. } catch (Exception e) {
12.  return 20;
13. }
14.  finally(){
15.  return 30;
17. }   
18.  
19. }
20.     
21.     
22. public static void main(String[] args) {
23.         
24.  TryCatchReturn obj = new TryCatchReturn();
25.        
26.  System.out.println(obj.calc())
27. }
28. 
    
29. }

Output:

1. 30

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